Wettability refers to the tendency of a solid to be in contact with one fluid rather than another. In wellbore drilling applications, the fluid phases may be water, oil, and/or gas while the solid phase may be the minerals that make up the reservoir rock. The wettability of reservoir rocks is known to affect the hydrocarbon distribution within a subterranean formation and impact many aspects of reservoir engineering such as hydrocarbon recovery, multiphase fluid flow, and formation pressure. Wettability may also affect formation resistivity and dielectric properties.
Reservoir wettability may be measured using conventional laboratory techniques, for example, Amott imbibition measurements or U.S. Bureau of Mines centrifuge capillary measurements may be made on formation cores (also referred to as plugs). While these techniques are industry recognized, they can be overly sensitive to numerous factors and are generally very time consuming (e.g., sometimes requiring many weeks to obtain a reliable wettability measurement). These measurement techniques also generally require significant sample conditioning (e.g., repeated cleansing, flushing, and rinsing) which is time consuming and may cast doubt on the obtained wettability values.
Nuclear magnetic resonance (NMR) measurements that derive wettability from one dimensional T1 and/or T2 spectra have also been disclosed (e.g., in commonly assigned U.S. Patent Publications 2013/0261979 and 2013/0325348). One challenge in using these 1-D NMR methods is that they tend to require accurate knowledge of bulk relaxation times and volumes (or Sw) for all fluids, the surface relaxivity, the pore size distribution, and the separation of individual fluid responses. These methods can also be time consuming in that they may further require multiple step data acquisition and extensive sample conditioning. Therefore, there remains a need in the art for improved wettability measurement techniques.